Computer Science 322 Operating Systems Mount Holyoke College Spring 2008

Agenda

• Announcements
  • To move grading along, I would like you to demonstrate your shells over the next week or so.
  • Term project proposals are your main focus this week: talk to me soon, since I'm at a conference at the end of the week.
• Next week: Exam 2
  • 47:10 take-home from end of class 4/14, to start of class 4/16
  • same ground rules as previous exam
  • Topics:
    • semaphores
    • synchronization problems
    • monitors
    • Unix systems programming (the things you've used for the shell)
    • deadlock
    • memory management up to what we cover today
  • Practice exam out - ask questions about this on Wednesday!
• Memory management
  • Paging
    • break up logical memory into pages, physical memory into frames
    • page size: the size of these pages/frames
    • can allow virtual memory
    • translate addresses by looking up a frame number using the page number, which is part of the logical address
    • store the translations in a page table in memory
    • a memory access now requires a page table access then the memory access - slow!
    • help: translation lookaside buffer - associative memory that stores a subset of table entries
    • TLBs are small, but locality helps it to have an excellent hit rate in practice
    • page table too large? page it - multilevel page tables
    • another option: inverted page tables
    • memory protection with paging: valid/invalid bits
    • shared pages

Lecture Assignment

Turn in a short answer to question 8.9 in SG&G. Please turn in a hard copy (typeset or handwritten are OK) at the start of class on Wednesday, April 9. We will discuss the question during class, so no late submissions are accepted.

Also, please take a look at the practice exam questions.